Vacuum circuit breaker



Dec. 8, 1931.

R.PELLNHHD ET'AL VACUUM CIRCUIT BREAKER Filed June 2s, 1928 ATT'ORNEYPatented Dec. 8, 1931 marre 'RUDOLF HELLMUNI), 0F SWISSVAII'JE, AND

PENNSYLVANIA, ASSIGNORS TO WSTINGHOUSE'ELECTRIC D MANUFACTURING smreal'PATENT oFrIcE ROBERT C. DICKINSON, E WILKINSBURG,

COMPANY, A CORPORATION 0F PENNSYLVANIA vacuum cmcurrnnmxnn Applicationlled June 23,

Our invention relates to circuit breakers and particularly to enclosedcircuit breakers in which the contactsthereof are separated in a vacuum.

An object of our invention is to provide a circuit breaker of the vacuumtype wherein 'access to the interior of the circuit-breaker housing forthe purpose of inspection or repair may be conveniently obtained andwherein the construction of the circuiti usually employed in vacuumcircuit breakers `A further object of our invention is to provide acircuit breaker of the vacuum type wherein the circuit-breaker operatingmember is pivotally mounted on the circdit-I breaker housing and whereinthe opening through which the operating member extends, is sealed bymeans of a vsylphon connected to the housing and to the operating memberand laterally displaceable Yby the operating member in order to minimizedei flection of the walls of the sylphon and to obtain a maximumopeningmovement of the circuit breaker contacts.

These and other objects that will be made apparent throughout the'further description of -our invention are attainedv by means of theaparatus hereinafter described and illustrated in the accompanyingdrawings,l wherein Figure 1 is a side view of a circuit breakerembodying features of our invention, and

Fig. 2 is a longitudinal section through the circuit breaker shown inFig. 1 taken on the line II-II thereof.

Referring to the drawings lthe circuit breaker apparatus'comprises ametal housing 3 provided with a metal cover 4 that 192s. serial No.287,805.

is welded at 5to the side walls of the housing. The cover 4 is providedwith an opening 6 through which the stationary contact member 7 of thecircuit breaker extends into the housing. The contact member 7 issupported upon` a conducting rod 8 that is secured to a cover plate 9which serves to close the opening 6. The rod 8 is provided with aterminal 11 to which one of the conductors, (not shown), may beconnected in the usual manner. f

The cover 9'is insulated Jfrom the `cover 4 by means of a porcelain orglass insulating bushing 12, and a non-rigid seal is provided 'betweenthe plates 9 and 4 for preventing injury to the bushing by insertinglead packing washers 13 and 14 between the said plates and the ends ofthe insulating bushing. Flexible annular flanges 15 and 16 are solderedto the ends of the insulating bushing and to the plates 9 and 4,respectively, in

which annular grooves 20 are provided for receiving the solder thusforming a gas-V tight closure for the opening 6 in the housing, andlinsulating the stationary contact member 7 from the housing.

A movable contact member 17 is mounted upon an operating member 18 thatis pivotally carried byfa bracket 19 having an annular ilange 21 weldedto the side wall of the housing 3. ,The operating member 18 eX- tendsthrough the opening 22 that is partiallyclosed by the bracket 19 and isprovided with a threaded socket 23 for receiving the threaded end of aninsulating operating arm 24. A flange sleeve 25 is welded to theoperating member 18, and the opening 22 is sealed by means of a metalsylphon or bellows 26 that is welded tothe bracket collar 21, at oneend, and to the flanged sleeve 25 at the other end, thus making agas-tight joint at the place of emergence of the operating member fromthe casing 3.

A'lexible conductor. 27 is clamped, at one end, to the contact member 17by means of a clamp 28 and, at the other end, to a terminal 29 by meansof a clamp 31. It will be noted that the terminal 29 'is conductivelyconnected to the housing which may be grounded, if desired.1

The condition of the contacts may be determined by viewing them. througha glass 'window 32 that serves to close an opening 33 in the housing 3.A flanged bushing 34 is Welded to the casing 3, andthe window 32 issupported .by the packing gasket 35 that are retained in place by ametal ring 36 and screw clamps 37 having adaptable screws 38 engagingthe outer face of the flange of the bushing 34.

Vents 30 and'30a are provided in the covers 9 and 4, respectively, whichestablish communication between the interior of the housing 3l and* thespace between the packing washers 13 and f14, respectively, and theiexible ianges 15 and 16, respectively, for balancing the pressure onboth sides of the washers and relieving them from stresses incident tothe low pressure withinthe housing.

The cover 9 is retained in position by stud bolts 10 threaded into lugsl0a and the bolts 10 are surrounded by insulating bushings 1017 thatextend through openings in the cover 9 and insulating spacing bushing10. The cover 9-is, therefore, insulated from the cover 4.

It will be understoodthat it is desirable to maintain a vacuum in thethe order of .001 millimeters or less of mercury within the casing atall times. Ordinarily, the metal housing will be made sutliciently tightvagainst leakage to maintain the vacuum, but, when desirable, anysuitable exhaustf means, such a vacuum pump or a vaporizable chemicalgetter, may be provided to assist s uch mantenance.

It has been found that-the bombardment of electrons emanating from theelectrodes or contacts or conductors thereof detrimentally affect thelead gaskets 13 and 14 because the distance between the contactconductors 8 and the inner edges of the gaskets 13 and 14 is greaterthan the mean free path of the electrons. When electrons are dischargedin a container wherein a rare atmosphere is maintained, and arepermitted to move unobstructed, their velocities become exceedinglyhigh, and when they have been permitted to move substantially throughtheir mean free path, their` collision with molecules of the atmosphereis practically certain to cause further electrons to be released. Thereleased electrons move at terrific velocities. When such electronsstrikea metal surface, the molecules at`the immediate surface are alsoexploded and the metal vaporized. The electrons discharged from theconductor, if

Hthey do not collide with molecules of the atmosphere, collide withthewalls of the con-v tainer athigh destructive velocity and causevolatilization of the metal. Vaporized f metal released from the gasketsand elsewhere in the casin ordinarily, is deposited upon the inner suraces of the insulator bushform of a spool within the insulating bushing12, the lower 'flange 41 thereof, being clamped between the cover 4 andthe lead gasket 14 andV insulated from the conducting rod 8, therebyshielding the gaskets and insulating bushing from the moving electrons.The distances between the cylindrical portion of theshield and theconducting rod 8 and between the end portion of the shield and cover 9are considerably less than the mean free path of the electrons. It hasbeen found that the interference afforded by the shield preventsnumerous coll1sions with the molecules of the atmosphere within thecontainer and the attaining of destructive velocities and protects thelead gaskets from the bombardment of electrons, thereby preventingdeposit of metal upon the interior lof the insulator bushing 12.

Itwill be noted that, by reason of the `the contact 17 for opening thecircuit, with a minimum deflection of lthe bellows walls and,consequently, the life of the bellows is materially increased. While vWehave illustrated but one embodiment of our invention, it will beapparent to those skilled in the art that various changes,modifications, substitutions, additions'and omissions may be made in theapparatufs illustrated without departing from the spirit and scope ofour invention, asset forth in the appended claims.

We claim as our invention: 1. A vacuum circuit breaker comprising ahousing for containing a rareied atmosphere, a contact member within thehousing, a movable switch member within the housing for engaging. thecontact member and extend- A ment of the switch member.`

2. A vacuum circuit breaker comprisinga metal housing having an openingtherein, a contact member the housing, a conducting member for thecontact member extending through the said. opening, a closure for theopening for supporting the conducting member, an insulating* bushingsurroundc operating with the rst contact mem er, and

ing the conducting member for supporting the closure and for insulatingthe closure from the housing, a second contact member conductivelyconnected to the housin for coa metal shield surrounding the conductingmember and insulated therefrom, and disposed between the conductingmember and the interior of the said bushing for intercepting electronsdischarged from the said conducting member.

3. A vacuum circuit breaker comprising a metal housing having an openingtherein, a

contact member within the housing, a conducting member for the contactmember extending through the said opening, a closure for the opening forsupporting the conducting member, an insulatino' bushing surrounding theconducting mem er for supporting the closure and for insulating theclosure :from the housing, non-rigid metal washers disposed between theends of the bushing and the housing and closure member respectively, Ameans insulated from the closure member for clamping the closure inoperative relation to the housing, a second contact member consubscribedour names this 15th day of June,

ductivel'y connected to the housing for cooperating with the firstcontact member, and a metal shield surrounding the conducting member forintercepting the electrons discharged, from the conducting member andpreventlng the collision of the electrons with the said washers.

4. 'A vacuum circuit breaker compris/ing a` metal housing having acontact member conductively connected thereto and provided with anopening a cover for the opening, an insulating cylindrical bushingaligned with the opening and disposed between the cover and thehousing,` malleable metal sealing washers disposed at the ends of saidbushing and constituting a gas-tight seal between the bushing and thehousing and cover, re-

spectively, a second contact member conductively carried by the coverand extending Athrough the said bushing, and a cylindrical the interior'of said bushing and the said shield insulated from and surrounding thesecond contact and having a flange at its innermost end clamped betweenthe innermost washer and the housing for intercepting the electronsdischarged from the second contact member and preventing their collisionwith washer.

In testimony whereof, we have hereunto 192s. 'RUDOLF HELLMUND.

ROBERT o. picKiNsoN.

